赤泥中有价金属提取的进展

随着氧化铝工业的发展,赤泥的堆放及危害已成为日益严重的环境问题,如何有效地利用赤泥已刻不容缓。介绍了赤泥的基本性质,国内外赤泥在有价金属回收方面的研究进展,并通过火法和湿法两方面对赤泥的有价金属回收进行了阐述。火法中还原焙烧——磁选工艺和直接还原进行铁元素的提取;湿法中采用盐酸和硫酸酸洗浸出提取钪、钛、铁元素;以及近些年,通过高梯度脉动磁选机,直接磁选出赤泥中的赤铁矿,均为回收赤泥中的有价金属提供了有效途径。     

从赤泥中回收氧化钪的技术研究现状

赤泥是拜耳法生产氧化铝过程中的碱性固体废弃物,大量堆存对生态环境带来了严重的安全隐患,但其含有氧化钪等多种有价金属,是一种可利用的二次资源。介绍了国内外从赤泥中回收氧化钪的方法,主要包括酸浸工艺、碱浸工艺和生物浸出工艺,并对这些方法的技术原理和特点进行了分析和评述,指出了从赤泥中回收氧化钪的发展前景。     

从赤泥中提取钪的工艺现状

本文对国外从赤泥中提取钪的方法进行了简要的介绍,并对其浸出、萃取、粗提的主要工艺进行了总结,最后结合赤泥综合利用,提出了比较适宜的工艺流程。     

基于直接还原熔分的高铁赤泥综合利用试验研究

采用基于直接还原熔分的珠铁工艺处理高铁赤泥,并通过热力学分析和实验室试验进行了验证,试验结果表明:对于山东茌平某铝厂产的高铁赤泥,采用无烟煤为还原剂、CaF2为添加剂,用高温硅钼炉模拟转底炉,当赤泥与煤粉的配合比分别为85.6％和14.4％、添加剂为赤泥和煤粉总量的2％时,含碳球团在1400℃焙烧12min可实现渣铁分离,所得珠铁和渣可分别用作钢铁冶金和浸出钪的原料.     

赤泥中回收稀土金属的综述

叙述了从赤泥中稀土金属回收的意义以及我国赤泥中稀土元素的赋存状况.介绍了国内外从赤泥中回收稀土元素的工艺,并对其进行了评述.针对我国山西铝厂的赤泥中含钙和钠较高的特点,提出了先焙烧,再用盐酸浸出稀土,然后在浸出液中加碱,得到钪等稀土金属氧化物沉淀,最终分离的新工艺.该工艺能有效分离稀土,易实现工业化生产,废水处理量少,不产生新的污染,符合节能和环保的要求.但是目前还停留在实验室阶段,要实现工业化生产,其经济效益如何有待于进一步的实践证明.     

从赤泥中浸出微量元素钇的工艺研究

通过对某厂拜耳法生产氧化铝副产物赤泥中钇的酸浸工艺条件及动力学研究,同时考察了赤泥粒度、浸出温度、液固比及酸浓度对微量钇浸出率的影响,建立了钇的酸浸动力学模型。试验结果表明:在赤泥颗粒大小140目、反应温度85℃、液固比4:1、酸浓度10%时,钇的浸出率可达80%以上,同时对试验数据处理分析,得出钇的浸出符合固体产物层内扩散控制模型,动力学方程为:1-(1-X_B)~(2/3)-2X_B/3=kt,活化能为16.24k J/mol。     

赤泥综合利用技术研究

根据赤泥中各金属离子化学活性的不同,分别用不同浓度、不同种类的酸对赤泥进行分步浸出,使赤泥中的各金属离子得到初步分离。再分别对浸出液进行处理以得到氧化钪、氧化钛等产品,其纯度分别在97%和95%以上。三次酸浸赤泥渣可以配料生产高标号水泥,实现了赤泥综合利用的目的。     

赤泥盐酸浸出钇试验研究

赤泥是一种含有稀贵金属的二次矿产资源,本文提出了赤泥盐酸浸出钇的方法。研究了盐酸浓度、浸出温度、液固比、搅拌速率和反应时间等工艺参数对钇浸出率的影响。通过ICP-AES和XRD分析,探究赤泥盐酸浸出过程的物相变化和作用机理。结果表明,在盐酸体积浓度为30%、浸出温度为100℃、液固比为7 m L/g、搅拌速率为300 r/min和反应时间为60min的条件下,钇浸出率可达83%,此过程中钙霞石和方解石几乎全部溶解,赤铁矿和钙钛矿部分溶解,板钛矿和石英则没有溶解。     

云南某赤泥还原焙烧-磁选试验研究

赤泥是氧化铝生产过程中产生的一种碱性固体废弃物。本论文研究了直接还原焙烧-磁选工艺回收赤泥中的铁。在对赤泥原矿进行一系列测试分析的基础上,分别研究了反应时间、反应温度、还原剂的种类及用量,添加剂的种类及用量与磁选场强对试验结果的影响,并对添加剂的作用机理进行了一定的分析。研究发现,在活性炭:CaF_2∶NaF:赤泥=16∶12∶12∶100,焙烧温度1150℃,焙烧时间120min的条件下进行铁的还原焙烧,经水淬冷却后,磨矿时间10min,在磁选场强为2.0A(1940 Oe)的条件下进行磁选,最终可得到品位和回收率分别为81.75%和85.96%的铁精矿。     

赤泥中钠元素回收的研究

采用柠檬酸对赤泥中的金属元素进行浸出,生成的柠檬酸钠在食品、医药、环保和电镀等行业应用广泛,具有很好的经济效益。实验通过考察浸出温度、浸出时间和柠檬酸添加量对钠、铁、铝、钙等元素浸出率的影响,并进行正交实验,确定柠檬酸浸出赤泥中钠元素最佳条件。用碳酸钠对浸出液中的少量铝、铁、钙进行去除,得到纯净的柠檬酸钠溶液。     

Selective Dealkalization of Red Mud Using Calcium Oxide with Pressure Leaching

Selective leaching of Na from red mud by using CaO with pressure leaching was investigated. The main factors studied were temperature, pressure, CaO dose, and leaching time. An L₉(3⁴) orthogonal test was carried out to analyze the importance of each factor and define optimal conditions. The leaching mechanism of sodium was investigated and analyzed using inductively coupled plasma–atomic emission spectrometry, x-ray diffraction, and scanning electron microscopy with energy-dispersive spectrometry. More than 85% of sodium could be dissolved under the optimal conditions. The order of influence of the investigated factors on the leaching efficiency of sodium was CaO dose?>?liquid-to-solid ratio?>?leaching time?>?leaching temperature/pressure. Cancrinite was decomposed from the red mud during the selective leaching process. The decomposition products silicon oxide and aluminum oxide reacted with calcium oxide, and the reaction products calcium silicate and calcium aluminate remained in the leaching residue. However, the other decomposition product, i.e., sodium oxide, was dissolved in the leaching solution. Other components in the red mud underwent almost no change in the process, representing an advantage compared with other processes that have been proposed.     

Recovery of scandium from bauxite residue——red mud:a review

Red mud is a slimy caustic residue generated from alumina production. Taking into account the relatively considerable content and availability of scandium, red mud can be viewed as an important and promising scandium resource rather than a solid waste. This paper is primarily to review the investigations of scandium recovery from red mud based on the most widely used hydrometallurgical processes including acid leaching, solvent extraction and ion exchange adsorption. It is thought that recovery of scandium from red mud should be considered as a direct objective rather than a by-product in the development of overall flowsheet. In order to achieve environmentally-friendly processes with high scandium recovery and low cost, more attention is required to be paid to optimizing the selective leaching of scandium to decrease mineral acid consumption and alleviate pollution, and developing new solvent extraction systems and novel ion exchange adsorption materials with high selectivity and recognition for scandium.     

Recovery of alumina and ferric oxide from Bayer red mud rich in iron by reduction sintering

A great amount of red mud generated from alumina production by Bayer process not only threatens the environment but also causes waste of secondary resources. High-iron-content red mud from Bayer process was employed to recover alumina and ferric oxide by the process of reduction-sintering, leaching and then magnetic beneficiation. Results of thermodynamic analyses show that ferric oxide should be reduced to Fe if reduction of ferric oxide and formation of sodium aluminate and calcium silicate happen simultaneously. Experimental results indicate that alumina recovery of Bayer red mud can reach 89.71%, and Fe recovery rate and the grade of magnetite concentrate are 60.67% and 61.78%, respectively, under the optimized sintering conditions.     

Recovering metals from red mud by thermal treatment and magnetic separation

This paper deals with an alternative treatment for recovering metals from goethite red mud (RM), which occurs as a by-product at zinc leaching plants. It is derived from the hydrometallurgical treatment of sphalerite, which involves roasting followed by acid attack and subsequent recovery of the zinc by electrodeposition. The leaching mud contains various oxides and hydroxides of iron plus lesser amounts of sulfates of Pb, Zn, Ca, Cd, Ag, In, Se, and other metals. In recent years, numerous attempts have been made to recover the RM or render it inert, particularly by such processes as vitrification or lithification for the production of glass ceramics. The work reported here proposes a treatment involving reduction and magnetic separation to permit the extraction of pure zinc, a high percentage of a pure magnetite, and a harmless slag containing mixed silicates of zinc and lead as well as oxides of minor elements.     

INFLUENCE OF ADDITIVES ON SLAG－IRON SEPARATION DURING DIRECT REDUCTION OF COAL－BASE HIGH－IRON－CONTENTREDMUD

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郑州氧化铝厂赤泥化学和矿物学特征及资源化利用探讨

研究了郑州长城铝业有限公司氧化铝厂所排放的拜耳-烧结联合法赤泥的基本化学和矿物学特征。选取新鲜、五年堆期和十年堆期的赤泥,分析项目包括pH、EC、水溶性和交换性盐基离子、X射线衍射矿物分析等。此外,还采用为期两年的慢速接力滴定法对这三种不同堆期赤泥的酸中和容量进行测定。选取酸中和能力最强的新鲜赤泥作改良剂,检测其作为改良剂对消除酸性矿山土壤酸性、降低土壤重金属活性和促进植物生长的效果。     

赤泥最佳热处理工艺制度研究

研究了不同煅烧恒温时间和不同冷却制度对赤泥胶凝性能的影响，并借助胶砂强度试验和DTA，XRD等一系列分析方式对热活化后赤泥的胶凝性能进行了分析。结果表明：采用空气中自然冷却的方法，恒温时间从1h～3h，赤泥的活性随恒温时间的增长而增加较快，恒温3h后活性增加较缓；采用随炉缓慢冷却的方法，恒温2小时的赤泥较恒温1h有明显增加，恒温2h后活性增加缓慢。空气中自然冷却和随炉温缓慢冷却这两种冷却制度对赤泥的活性影响也较为显著。     

Surface charge properties of red mud particles generated from Chinese diaspore bauxite

Acid/basic potentiometric titration can be used to quantify the red mud surface charge properties. The amount of surface active --OH groups and surface charge density on the red mud particles generated from Chinese diaspore bauxite were evaluated from the acid/basic potentiometric titration data in 0.1 mol/L or 0.5 mol/L NaCl solution. The results show that the adsorption of sodium polyacrylate（SPA） on the red mud surface causes the increase of the surface active --OH groups, which makes the point of zero charge（PZC） shift to a lower pH value. However, the adsorption of polyacrylamide（PAM） causes little change. As the concentration of NaCl solution increases, the surface charge becomes more positive in acidic solution and more negative in alkaline solution, which can be attributed to the presence of a porous surface gel coating on the red mud particles.